Traveling wave tube (twt) oscillation prevention device

ABSTRACT

A traveling wave tube amplifier device which suppresses random oscillations through the entire length of the traveling wave tube. The solid side walls have a series of resonant slots which are structurally coupled to one another through the wall and lossy load along the entire length of the traveling wave tube. The slots are resonant at a frequency above the operating band of the tube, but below the lower edge of its stop band.

Unite tates Patent Scott et al.

[54] TRAVELING WAVE TUBE (TWT) v OSCHLLATION PREVENTION DEVICE [72] Inventors: Allan W. Scott; Yukio Hiramatsu,

both of Los Altos, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: May 3, 1971 [21] Appl. No.: 139,332

[52] US. Cl ..3l5/35, 315/393, 333/31 A [51] Int. Cl. ..H0lj 25/34 [58] Field oi Search ..3l5/3.5, 3.6, 39.3; 333/31 A [56] References Cited UNITED STATES PATENTS 3,221,205 11/1965 Sensiper ..3l5/39.3 X 3,221,204 11/1965 Hant et al. ..315/39.3 X

i151 3,693,038 51 Sept. 19, 1972 3,505,730 4/1970 Nelson ..29/600 3,504,223 3/1970 Orr et a]. ..315/3.5 3,360,679 12/1967 Rubert ..3 15/35 3,365,607 l/l968 Ruetz et al ..3l5/3.5 3,387,168 6/1968 Beaver; ..3l$/3.5

Primary Examiner-Herman Karl Saalbach Assistant Examiner-Saxfield Chatmon, Jr. AttorneyR. S. Sciascia and Charles D. B. Curry 5 7 ABSTRACT A traveling wave tube amplifier device which suppresses random oscillations through the entire length of the traveling wave tube. The solid side walls have a series of resonant slots which are structurally coupled to one another through the wall and lossy load along the entire length of the traveling wave tube. The slots are resonant at a frequency above the operating band of the tube, but below the lower edge of its stop band.

10 Claims, 4 Drawing Figures PATENTEDSEP 19 I972 PHASE SHIFT PER PERIOD BACKGROUND OF THE INVENTION l Field of the Invention The present invention relates generally to a traveling wave tube oscillation prevention device and more particularly to a device which suppresses extraneous oscillations through the entire length of the traveling wave tube, hereinafter referred to as TWT.

2. Description of the Prior Art The prior devices for suppressing spurious oscillations in broadband T-WTs controlled extraneous oscillators at the inputs of the tubes and not through the entire length of the TWT. Moreover, the prior TWTs, especially high power tubes, have a proclimity to oscillate at frequencies near the edge of the passband. It has been found that by replacing the solid side walls along the entire length of the TWT shell with resonate slots, the oscillations are dampened out through the entire length of the TWT. This technique enables the TWT to attenuate energy at the resonate frequency of the tube. This unique device is capable of attenuating energy at the frequencies where the tube is most likely to oscillate, but without affecting the energy at frequencies along the passband.

STATEMENT OF THE OBJECTS OF INVENTION The major object of the present invention is to provide a device which will dampen out random oscillations of a TWT along the entire length of the TWT.

Another object of the present invention is to provide a means that will effectively attenuate energy at the resonate frequency of the TWT.

Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graphic representation showing the phase shift as a function of frequency;

FIG. 2 is a sectional view of the TWT device;

FIG. 3 is a longitudinal sectional view of the two sections of the ring bar circuit; and

FIG. 4 is an end view of ring bar circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 wherein the crosshatched area 0,, represents the operating band of the tube, Points a, c on Curve A and Point b on Curve B represent selected oscillation frequencies. The device represented in FIGS. 1 and 2, including the comb supported ring bar helix, is designed to be used as an amplifier. The oscillations occur at the lowest voltages at the upper end of the stop band.

Referring to FIG. 2 wherein the oscillation suppressor device 11 comprises tube shell 13, wall structure 13a resonant slots or vertical slotted walls 15, ceramic waveguide 17, and ceramic support structure 23 of ring bar circuit 19, tube shell 13 is a rectangular shaped hollow-box-like structure. The hollow longitudinally extending portion of shell 13 forms the waveguide 17. Waveguide 17 is made of ceramic or other similar attenuation material. The vertical side wall 13a of tube shell 13 has a plurality of vertical parallel resonant slots 15 extending longitudinally along the side wall 13a and perpendicular to the top portion 13b and bottom portion 13c of tube shell 13.

Referring to Fig. 3 wherein the ring bar circuit 19 comprises two ring bar helix halves 21, ceramic support structure 23 forms a plurality of convoluting diametrically opposed U-shaped vertical walls 25. Ring bar I helix halves 21 each comprises a plurality of convoluting diametrically opposed U-shaped structures forming semicircles contoured to fit in the plurality of vertical half-circles apertures 25a of support structure 23.

Referring to FIGS. 1, 2, and 3 wherein ceramic support 230 and 23b are brazed to shell 13 only at the top 13b and bottom of shell 13, the vertical walls 25 are added later to make the complete assembly. To add oscillation suppression, a solid sidewall which has been used in prior systems is replaced with a special wall 13a in which a plurality of vertical resonate slots 15 are cut. The slots 15 are resonate just below the lower edge of the stop band, but above the operating band of the tube. The slot period is the same as the period of the slow wave structure. Below the resonate frequency of the slots 15 that is in the operating band 0 of the tube, the slotted walls 15 appear as a solid microwave wall and no changes occur in the circuit characteristics. However, at and above the resonate frequency of the slot 15 energy is coupled from the circuit through the slots 15 into the ceramic waveguides 17 outside the wall. See FIG. 1. The ceramic in waveguide 17 has been coated with a sputtered attenuator material to make the waveguide lossy. In this way, a region of high loss is introduced, which is not coupled to the circuit in the operating band 0,, of the tube, but does couple in the .is required to completely suppress all oscillations,

slotted walls A can be located on both sides of the circuit rather than just on one side. That is, another similar structure may be located on the other side of the circuit 19. The slots 15 on both sides are structurally coupled to one another through the wall 25 and lossy load 17 along the entire length of the TWT.

Moreover, when the slots 15 become resonant at a frequency above the operating band 0,, of the tube, but below the lower edge of the stop band, the slotted walls 15 appear solid on the operating region of the tube, but oscillations above the operating range of the TWT are coupled through the wall 25 and into the ceramic waveguide 17 which has been coated with an attenuation material. Thus, the oscillations are coupled to lossy load and are thereby dampened out.

What is claimed is:

1. A device for suppressing spurious oscillations along the entire length of a comb supported ring bar circuit, said ring bar circuit including a plurality of individually spaced convoluting diametrically opposed vertical walls attached between an upper and lower supporting means, said device comprising in combination:

a. a rectangularly shaped continuously hollow means for propagating electromagnetic wave energy;

b. said plurality of individually spaced vertical walls being spaced apart so as to form a plurality of separate partitions;

c. said propagating means having vertical apertured side walls forming a plurality of resonant slots; and

d. said propagating means being longitudinally and structurally coupled directly to said upper and lower supporting means so that said plurality of partitions directly oppose said plurality slots, slots said slots being coupled to one another through said hollow means.

2. The device in claim 1 wherein said apertured side walls have an upper wall-portion and a lower wall-portion for each aperture.

3. The device in claim 2 wherein said propagating means is structurally coupled to said ring bar circuit at said upper wall and said lower wall of each aperture.

4. The device recited in claim 3 wherein said propagating means is an elongated hollow rectangular shell attached to said ring bar circuit.

5. The device recited in claim 4 wherein said hollow rectangular shell is a waveguide coupled to the vertical outside walls of said ring bar circuit.

6. The device recited in claim 4 wherein said shell has resonant slots on one side of said ring bar circuit.

7. The device recited in claim 6 wherein a said shell is located on both sides of said ring bar circuit.

8. The device recited in claim 5 wherein said hollow shell of said waveguide is coated with a ceramic attenuation material to form a lossy load.

9. The device recited in claim 8 wherein ceramic waveguide is brazed to top and bottom support structures of the ring bar circuit.

10. The device recited in claim 9 wherein said ring bar circuit is coupled to said waveguide said waveguidecomprising a plurality of resonant slots with upper and lower slot portions operatively connected to the sidewalls of said ring bar circuit. 

1. A device for suppressing spurious oscillations along the entire length of a comb supported ring bar circuit, said ring bar circuit including a plurality of individually spaced convoluting diametrically opposed vertical walls attached between an upper and lower supporting means, said device comprising in combination: a. a rectangularly shaped continuously hollow means for propagating electromagnetic wave energy; b. said plurality of individually spaced vertical walls being spaced apart so as to form a plurality of separate partitions; c. said propagating means having vertical apertured sIde walls forming a plurality of resonant slots; and d. said propagating means being longitudinally and structurally coupled directly to said upper and lower supporting means so that said plurality of partitions directly oppose said plurality slots, slots said slots being coupled to one another through said hollow means.
 2. The device in claim 1 wherein said apertured side walls have an upper wall-portion and a lower wall-portion for each aperture.
 3. The device in claim 2 wherein said propagating means is structurally coupled to said ring bar circuit at said upper wall and said lower wall of each aperture.
 4. The device recited in claim 3 wherein said propagating means is an elongated hollow rectangular shell attached to said ring bar circuit.
 5. The device recited in claim 4 wherein said hollow rectangular shell is a waveguide coupled to the vertical outside walls of said ring bar circuit.
 6. The device recited in claim 4 wherein said shell has resonant slots on one side of said ring bar circuit.
 7. The device recited in claim 6 wherein a said shell is located on both sides of said ring bar circuit.
 8. The device recited in claim 5 wherein said hollow shell of said waveguide is coated with a ceramic attenuation material to form a lossy load.
 9. The device recited in claim 8 wherein ceramic waveguide is brazed to top and bottom support structures of the ring bar circuit.
 10. The device recited in claim 9 wherein said ring bar circuit is coupled to said waveguide said waveguide comprising a plurality of resonant slots with upper and lower slot portions operatively connected to the sidewalls of said ring bar circuit. 